Travelling wave tubes



Jun 1963 J. M. WINWOOD ETAL TRAVELLING WAVE TUBES Filed Nov. 13, 1959 FIG.2.

INVENTOR. J. M. WINWOOD J. P. BEASLE Y AGEN United States Patent O 3,095,521 TRAVELLING WAVE TUBES .John Morland Winwood, Salfords, and James Patrick Beasley, Langley Green, Crawley, England, assignors to North American Philips Company, Inc., New York,

This invention relates to a travelling-wave tube and is concerned with means for enabling a travelling-wave tube to be readily aligned within a magnet assembly such as is commonly used with such tubes.

In known arrangements the magnet assembly for a travelling-wave tube is provided separately from the tube and when assembling the equipment the tube is inserted into the field system. In order to ensure that the longitudinal axis of the travelling-Wave tube is aligned coaxially with the longitudinal axis of the magnetic field produced by the magnet assembly, the casing or support of this assembly is frequently provided with means, such as adjusting screws, whereby, after the tube has been inserted into the assembly, it may be adjusted angularly so as to align the axes of the tube and of the magnetic field. This method is frequently laborious and where it is necessary to replace a travelling-wave tube it is also necessary to re-ali-gn the new tube.

One object of this invention is to provide a travellingwave tube having means whereby the tube readily may be aligned with the axis of a magnet assembly adapted to be used with it.

In order that the invention may be readily understood and carried into effect two embodiments thereof will now be described with reference to the accompanying diagrammatic drawings wherein:

FIGURE 1 shows partly in cross-section the gun end of axtrauelling-wave tube, and

FIGURE 2 illustrates a tube located in position.

Referring now to FIGURE 1 a travelling-wave tube is provided with a glass envelope comprising a portion 2 of large diameter, a portion 3 of comparatively small diameter and a foot 9 through which extend connection pins 10. Within the portion 2 is disposed the electron gun 18 of the tube and Within the portion 3 is disposed the helical delay-line 19 of the tube.

The portion 3 of the envelope is made of precision-bore glass tubing and the delay-line is supported Within this bore, but although the bore of the portion 3 is precisionformed the outer surfaces of the portions 3 and 2 are not precisely located with respect to the bore 3.

In accordance with one embodiment of the invention a cylindrical surface 4 is ground on the outside of the portion 3, co-axial with the bore of that portion, this surface 4 being, of course, formed on the glass envelope portion 3 before the gun or the helix are inserted into the envelope and before the foot 9 'has been joined to the remaining portions of the envelope.

After this surface 4 has been formed the helix and the electron gun are inserted into the tube and subsequent stages of manufacture up to the final sealing-off are performed. At this stage the travelling-wave tube is inserted in a jig which is provided with a chuck which grips the portion 4. In fixed relation to this chuck the jig is provided with reference surfaces so disposed that when the tube has been gripped in the chuck and an end cap indicated at in the fi-gure is slipped over the end of the tube, the position of this cap is determined not by the external contour of the portion 2 of the tube but by the reference surfaces formed on the jig, the position of these reference surfaces being fixed relative to the surface 4 by means of the jig. The end cap, before being slipped 3,095,521 Patented June 25, 1963 over the end of the portion 2 of the tube, is coated on its interior with suitable cement and when the cap is located in position against the reference surfaces of the jig the whole arrangement of jig, tube and end cap is then treated so as firmly to cement the end cap 5 to the portion 2 of the glass envelope. After this cementing process is completed the tube with the end cap is removed from the jig and it will be appreciated that the end cap is now located precisely with reference to the internal precision-bore of the portion 3. The end cap is provided with precision surfaces 6 and 7 so that it is now a comparatively simple matter to provide, on the casing or support of the magnet assembly, surfaces which will mate with the surfaces 6 and 7 so as to locate the travellingwave tube precisely within the magnetic field system.

The above embodiment incorporates a ground surface 4 formed on the portion 3 of the tube envelope but alternatively a reference surface 8 may be formed upon the wider portion 2 of the tube envelope. In this second embodiment the surface 8 is again ground with reference to the bore of the portion 3 and the tube is again located in a suitable jig, the end cap being secured to the tube as described in the first embodiment.

Although FIGURE 1 shows, for convenience, an envelope having two ground surfaces 4 and 8, it will be understood that in practice it is only necessary to form one such surface.

In FIGURE 2 is diagrammatically illustrated the manner in which the tube is located against a portion 1 1 of the magnet assembly. As shown in this figure, the portion 11 has a bore which provides a cylindrical reference surface 16, this surface 16 being arranged so as to be co-axial with the central magnetic axis of the magnet assembly. When :the tube is placed in the magnet assembly the surface 6 on the end cap 5 of the tube fits closely inside the surface 16 so as to locate the helix of the tube co-axially relative to the magnetic field. Additional position-location is provided by the annular reference surface 7 which abuts against an annular reference surface 17 formed on the portion 11 of the magnet assembly.

What we claim is:

1. A travelling-wave tube comprising a glass envelope having a portion thereof formed of precision-bore glass tubing, a helical slow-Wave structure concentrically disposed within the said portion, a cylindrical reference surface concentric With the bore of the said portion formed on the exterior of said envelope, an end cap for said tube, a cylindrical reference surface on said end cap, the end cap being firmly secured to the glass envelope in such a position that the cylindrical reference surface on the cap is co-axial with the cylindrical reference surface formed on the glass envelope.

2. A tube as claimed in claim 1 wherein the end cap is provided with an annular surface in a plane normal to the axis of the cylindrical reference surface on the cap.

3. A tube as claimed in claim 1 wherein the cylindrical reference surface on the tube is formed on the precisionbore tubing portion.

4. A tube as claimed in claim 1 wherein the cylindrical reference surface of the tube is formed on the portion of the tube enclosing the electron gun.

5. In the method of making a travelling-wave tube having a slow wave structure for insertion within a mag net assembly provided with a cylindrical bore coaxial with the magnetic field produced with a magnetic assembly, the steps of forming on the outside of the envelope of the tube a cylindrical reference surface co-axial with the slow-Wave structure of the tube, and securing to the tube an end cap having a cylindrical surface also co-axial with said slow-wave structure so that when the tube is inserted into the said magnet assembly the cylindrical surface on the end cap fits closely within said cylindrical bore so as to be located co-axially therewith.

6. A method as claimed in claim 5 comprising so forming on said end cap and adjacent said cylindrical bore plane reference surfaces normal to said cylindrical surface and saidcylindrical bore respectively so that when the tube is inserted into the magnet assembly the said plane reference surfaces abut against each other so as to locate the axial position of the tube relative to the magnet assembly.

References Cited in the file of this patent UNITED STATES PATENTS Johnson July 1, 1930 Rogers Sept. 9, 1958 Lauer et al. Mar. 3, 1959 Geisler Mar. 24, 1959 Karp et al. Apr. 14, 1959 Klein et al. Oct. 13, 1959 Anderson Oct. 31, 1961 Wolktein et al. Feb. 6, 1962 

1. A TRAVELLING-WAVE TUBE COMPRISING A GLASS ENVELOPE HAVING A PORTION THEREOF FORMED OF PRECISION-BORE GLASS TUBING, A HELICAL SLOW-WAVE STRUCTURE CONCENTRICALLY DISPOSED WITHIN THE SAID PORTION, A CYLINDRICAL REFERENCE SURFACE CONCENTRIC WITH THE BORE OF THE SAID PORTION FORMED ON THE EXTERIOR OF SAID ENVELOPE, AN END CAP FOR SAID TUBE, A CYLINDRICAL REFERENCE SURFACE ON SAID END CAP, THE END CAP BEING FIRMLY SECURED TO THE GLASS ENVELOPE IN SUCH A POSITION THAT THE CYLINDRICAL REFERENCE SURFACE ON THE CAP IS CO-AXIAL WITH THE CYLINDRICAL REFERENCE SURFACE FORMED ON THE GLASS ENVELOPE. 